PROJECT SUMMARY/ABSTRACT The goal of this F31 fellowship is to prepare me to become an independent researcher who can effectively contribute to addressing the individual and social ecological contexts that place women at risk for opioid use and overdose in the postpartum period. In the United States, opioid use disorder (OUD) during pregnancy has quadrupled since 1999, with overdose becoming a leading cause of non-pregnancy related death among pregnant and postpartum women. While identifying and treating OUD during pregnancy is a public health priority, limited attention has been given to the overdose and hospital readmission risks among postpartum women (defined here as being within the first year after childbirth) with OUD. Epidemiological data suggest women are at highest risk of overdose 7-12 months post-delivery with rates 25% higher than at pre-conception. Less understood are the co-morbid health issues, systemic social conditions, and limited health and social services women with OUD continue to face in their communities after childbirth. Under the guidance of my mentorship team and enhanced by the training from this fellowship, I will utilize inpatient hospital data from the Pennsylvania Health Care Cost Containment Council (PHC4) to assess hospital readmissions among women with OUD within one year of childbirth. Data will be merged with community-level data sources, such as the U.S. Census and SAMSHA?s Behavioral Health Treatment Services Locator, to determine how community context impacts postpartum opioid outcomes. The Specific Aims of this study are to: 1) Identify subgroups of women with OUD at delivery at increased risk of overall and opioid-specific hospitalizations postpartum; 2) Examine the association between community-level factors and individual class memberships, as well as their independent effects on postpartum opioid-related hospitalizations; and 3) Examine the spatial distribution of hospital births and postpartum opioid-related readmissions among women with OUD, and identify the community factors associated with ZIP code-level counts of deliveries and readmissions. To accomplish the proposed research, I will implement a comprehensive training and mentorship plan that will build on my prior substance use knowledge, research experience, and doctoral training. Specifically, my Training Goals will focus on expanding my knowledge and/or skills in: 1) reproductive health and opioid use among pregnant and postpartum women; 2) social and ecological determinants of substance use; 3) latent class analyses; 4) multilevel analyses; and 5) spatial analyses. These goals will be accomplished through a range of coursework, seminars, clinical observations, conferences, journal readings, and tailored mentoring from a committed team of interdisciplinary researchers. Complemented by support from a dedicated research and training environment at the University of Pittsburgh Graduate School of Public Health, this fellowship will accelerate my trajectory in becoming an independent researcher focused on reducing inequities associated with maternal substance use.